Selectively treating portions of articles by exposure to a treating medium frequently requires masking the remaining portions of such articles. One of the exceptions to a requirement for masking articles prior to treating portions thereof is a treatment of end portions of elongate articles in a liquid. Such a treatment is frequently accomplished by suspending the articles to be treated above the surface of the liquid, such that only the end portions of the articles to be treated depend into the liquid.
When such a partial immersion of articles is used to treat predetermined portions of the articles, it becomes important to precisely control the immersion depth of the articles. In open vessels or tanks containing a stagnant liquid at a fixed level, articles are readily immersed into the liquid to a predetermined depth. A structure for supporting the articles relative to the liquid level is typically mounted in fixed relationship to the walls of the tank. Thus by adjusting the height of the articles and the liquid level with respect to the tank, the immersion depth of the articles is established.
When the treating liquid is not stagnant, as, for example, in an electroplating or electro-etching bath, wherein the electrolyte is typically recirculated, the height of a weir between the treating tank and an overflow tank typically establishes the liquid level in the treating tank. Of course, the liquid level resulting from such an overflow across a weir depends to some extent on the flow rate of the liquid removably across the weir.
Thus, when the articles are supported by a structure at a fixed height above the top of the weir, and the flow rate across the weir increases, the liquid level above the weir increases slightly with a related increase in the depth of immersion of the articles into the liquid. In addition to a change in the immersion depth of the articles because the liquid level has changed, the immersion depth sometimes changes only apparently because of ripples occurring on the surface of the liquid.
It is, therefore, desirable to provide a support for partially immersing articles into a liquid, such that the immersion depth of the articles is precisely controlled.